The present invention relates to an image developing apparatus for developing an electrostatic latent image in an image forming apparatus employing an electro-photographic method such as a printer and the like.
In an image forming apparatus employing an electro-photographic method, an image developing apparatus using a one-component developing agent (hereinafter referred to as (xe2x80x9ctonerxe2x80x9d) has so far been used. The image developing apparatus using one-component toner has such advantages as mentioned below when compared with one that uses two-component toner. First, it does not require a detecting device as well as a control device for a density of the toner. Secondly, it facilitates cleaning of a latent image carrying body without causing damage to a surface of it even if the latent image carrying body is cleaned with a plate-like resilient body after a visible image is transferred, since carrier does not stick to the latent image carrying body during the development. Thirdly, it can readily achieve a simplification and a reduction in size of the apparatus.
On the other hand of the above advantages, however, the image developing apparatus using one-component toner has a problem that toner not charged electrically leaks from ends of an image-developing roller, because it does not include a substance like the carrier in the two-component toner that is attracted to a magnet.
In the image developing apparatus using one-component toner, it is a common practice now to use an elastic foam material such as polyurethane foam or the like as means to seal in the toner. The elastic foam material provides an advantage of large elasticity, and thereby it can fill up easily spaces among the image-developing roller, a housing cassette, and a toner layer thickness regulating means (hereinafter referred to as xe2x80x9cbladexe2x80x9d).
In the case of using elastic foam material as the sealing means, however, it is difficult to seal a space having an acute angle. In particular, it is unable to fill a space in a shape of wedge formed between a rounded portion of the image-developing roller and another rounded portion of the blade. Furthermore, a position of the sealing means cannot be aligned properly with respect to the blade, since the sealing means is attached to the housing cassette. In addition, the sealing means cannot be easily attached to a proper position, as it expands when being attached.
Hence, the image developing apparatus using one-component toner still has the problem of leakage of the toner for the above reasons. Moreover, it also has another problem of poor productivity, since it requires a sealing member such as a sponge to be attached to an inside of the housing cassette.
An image developing apparatus in which a detachable sealing member is attached to a side of a blade is disclosed in U.S. Pat. No. 5,697,021, as a measure to cope with the above problems. In the above disclosure, however, the sealing member is fixed in a manner to make a close contact with a housing cassette. On the other hand, since the sealing member is attached to the blade, the blade is affected by the sealing member. As a result, it presents a disadvantage that a thickness of the toner layer on an image-developing roller becomes uneven.
It is therefore an object of the present invention to provide an image developing apparatus that can prevent the toner from leaking, and assure a stable thickness of the toner layer in the image developing apparatus equipped with a blade.
An image developing apparatus of the present invention comprises a photosensitive body, an image-developing roller (hereinafter referred to as xe2x80x9cdeveloping rollerxe2x80x9d), a toner feeding roller, and a housing cassette, whereon the developing roller and the feeding roller are mounted, for storing the toner. The image developing apparatus also comprises a plate-like blade mounted on the housing cassette in a manner to keep a pressed contact with the developing roller, a sheet member for preventing a leakage of the toner, and a toner sealing means constructed of an resilient material for preventing the toner from leaking.
The sheet member is arranged between a development area of the developing roller and a position of the pressed contact between the image-developing roller and the feeding roller, and stays in uniform contact along a longitudinal direction of the developing roller.
The toner sealing means is either mounted integrally to, or formed integrally with the blade as one unit, and is provided at each end of the blade. Further, a space is provided between the toner sealing means and the housing cassette.
The above structure of the present invention realizes prevention of the toner from leaking in the image developing apparatus, since it effectively fills a space located between the blade and the developing roller.
Furthermore, the structure also realizes an improvement of productivity and a reduction of working processes, since it makes an adhesion of the toner sealing means unnecessary in manufacturing the image-developing apparatus.